Metal waveguides are often used in high-power, low-loss applications, such as satellites, radar systems, and space craft. Electroless-plated, three-dimensional printed plastic parts are a lightweight option for the realization of waveguide circuits, but this technology suffers from limited power capability due to the low glass transition temperatures of the plastics and delamination issues. In addition, such parts exhibit higher loss as compared to solid metal waveguides. For high-power applications, and where loss is an important factor, solid metal waveguides are the option of choice although, but they are accompanied by higher weight and the need for greater amounts of material. In view of the above discussion, it can be appreciated that it would be desirable have high-performance, solid metal waveguides having less weight and requiring less material to construct.